Mr White, who comes from _____ European country, has formed ____ habit of attending  church on Sundays.

A．an; /

B．a; a

C．an; the

D．a; the

高压注水泵的叶轮一般采用（）材料。

A.铸钢

B.碳素钢

C.不锈钢

D.铸铁